Over the last decade, bicarbonate dialysates have become increasingly significant for use in hemodialysis. The most common of previous dialysates were based on acetic acid, which inherently provided a very stable, bacteria-static solution which could be handled and processed with relatively little concern over bacterial contamination of fluctuating pH levels. Despite how stable the acetate dialysates were, though, the hemodialysis patients who underwent their treatment were not -- it was quite common with acetate dialysates for patients to become nauseous and otherwise discomforted. Bicarbonate dialysates (i.e., dialysates having a bicarbonate base) were found to drastically reduce such patient discomfort and, consequently, most hemodialytic processes today employ bicarbonate dialysates.
Regardless of the type of dialysate, the preparation and delivery of solutions for use in dialysis has ordinarily been performed on a batch-by-batch basis, with the dialysate being prepared at the particular dialysis machine immediately prior to use. Such on-site preparation enables variation in the prescription of the dialysate from one patient to the next, which has become increasingly common. At the sacrifice of such flexibility, it has also been common to mix and test dialysates at a central location and then deliver it in separately sealed bottles to separate hemodialysis stations for prompt usage. In either case, the burdens of manual delivery, mixing, and the continuous need to replenish the bottles of dialysate solutions are readily appreciated by hospital technicians and others attending to such tasks and, as a consequence, to those responsible for administering hemodialysis services.
To alleviate analogous problems in other fields of dialysis, the mixing and distribution of dialysates has been relatively centralized and automated in some instances by supplying a pre-mixed dialysate through separate conduits from a bulk reservoir. Systems employing centralized peritoneal dialysate distribution, for example, have been referenced in McDonald, Harold, Jr., "Replacement of Renal Function", European Dialysis and Transplant Association. Vol. III, 1966, at pages 366-367. Other types of non-centralized but automated systems have also been known in the field of peritoneal dialysis, such as may be further evidenced in McDonald, Harold P., Jr., "An Automatic Peritoneal Dialysis Machine: Preliminary Report", Transamerican Society for Artificial Internal Organs. Vol XI, 1965, at pages 83-85. Such centralized systems, in theory, should provide for greater economies and greater time efficiencies in almost any large-scale system, but they are simply unworkable for centralized distribution of bicarbonate concentrate. In short, despite how elementary the general concept of centralized and/or automated bicarbonate concentrate delivery may be, the practical distribution of bicarbonate concentrates through such systems while maintaining required performance and safety standards has been extremely elusive.
Among the most critical of the difficulties which must be overcome to realize centralized distribution of bicarbonate concentrates relates to the inability to adequately control the acidity of bicarbonate concentrates and reduce micro-contamination thereof. The hydrostatic pressure required for a central distribution system having multiple outlets tends to produce greater flow velocities which, in turn, increase aeration of centrally-distributed bicarbonate concentrate. Turbulence created in mixing and circulating the bicarbonate concentrate also tends to increase aeration. Unfortunately, bicarbonate concentrates used in hemodialysis are especially susceptible to deterioration when aerated. Specifically, when bicarbonate concentrate is aerated, the CO.sub.2 of bicarbonate tends to be liberated by aeration of the bicarbonate and, consequently, the pH of the bicarbonate concentrate fluctuates drastically. Due in part to such bicarbonate concentrate deterioration, centralized distribution systems have long been unsuccessful for distributing bicarbonate concentrates.
One example of the costly failures of others in this field occurred several years ago in a Kansas City facility. In that case, a centralized bicarbonate bicarbonate concentrate distribution system was constructed with the goal of servicing multiple hemodialysis patients. Regretably, the system failed and the centralized aspects of the Kansas City facility had to be abandoned due to the inability to control the pH and micro-contamination of the bicarbonate concentrate -- naturally at a great loss to the hospital. Other attempts over the years have similarly failed and, consequently, the medical community has confirmed, re-confirmed, and finally conceded that such centralized bicarbonate concentrate distribution systems are simply unworkable on a practical basis.
Therefore and for still other reasons which will be apparent, it is an object of the present invention to provide a centralized bicarbonate distribution system which is capable of accommodating numerous stations without detrimental aeration of the bicarbonate. Another object is to provide for such distribution of the bicarbonate in a concentrate form so that it can be mixed with other ingredients according to varying prescriptions at different dialysis stations.
A countervailing consideration is the retarding of bacterial growth in the conduits of a centralized distribution system. To alleviate this problem in the field of peritoneal dialysis, centralized dyalisate distribution systems have been constructed wherein independent bicarbonate concentrate lines are selectively employed to service single peritoneal dialysis stations and, following such service, all the in-line bicarbonate concentrate is expelled through a drainage system as waste.
It is also a primary object of the present invention to minimize or prevent bacterial growth within systems constructed according to other objects of the invention, which includes preventing bacterial growth in the bicarbonate concentrates commonly employed today. Another object of the present invention is to enable centralized distribution of bicarbonate concentrate in a system which recirculates the bicarbonate concentrate from remote stations while also addressing other objects of the present invention.
Existing dialysis machines are limited to the extent of the pressure which they are capable of sustaining under normal operation. This is primarily due to the fact that they are designed to operate by drawing bicarbonate concentrate from a pre-mixed bottle, rather than a pressurized source. It has been found by Applicant that providing a line pressure greater than 15 p.s.i. tends to affect the dialysis operation in such conventional dialysis machines. Therefore, to accommodate presently available dialysis equipment, it is yet another object of the present invention to distribute diaylsate to multiple stations having conventional dialysis machines in a manner such that the bicarbonate concentrate is introduced to such machines at pressure levels which do not inhibit their operation. A related object of the present invention is to provide a centralized bicarbonate concentrate circulatory system for multiple stations which balances the object of maintaining bicarbonate concentrate pressures at operational levels for conventional dialysis machines while simultaneously addressing the other objects of the invention, including the objects of minimizing bacterial growth and controlling the pH and contaminant concentrations of the bicarbonate concentrate.
Moreover, it is an object of the present invention to provide a self-sterilizing bicarbonate distribution system or one which is capable of continual operation despite intermittent sterilization.
It is also an object of the present invention to enable achievement of all applicable hemodialysis standards in a centralized bicarbonate concentrate distribution system. Such standards have been emperically established by the medical community in general. Many of such standards are embodied in the AAMI 1982 Standards for Hemodialysis Systems published by the American Association of Medical Instrumentation (which are incorporated herein by this reference), and other standards of good workmanship known to those in the fields of the present invention.
Underlying each of the objects of the invention is the fundamental and pervasive object of providing better and perhaps more economical service to dialysis patients by overcoming the problems and deficiencies of the prior art. More particularly, it is an object of the present invention to provide a new and improved centralized bicarbonate concentrate distribution system and related methods for use in facilitating dialysis. Many other problems, obstacles and deficiences faced by the prior art and addressed by the present invention will be obvious to those skilled in that art, especially in light of the descriptions herein.